Field of the Invention
The present invention relates to a seal structure according to a sealing technique. The seal structure according to the present invention is used for sealing a section where three surfaces are joined together, for example, in an electric equipment device and an engine.
Description of the Conventional Art
In the electric equipment device such as an electronically controlled unit, a power control unit or a DC-DC converter for an electric vehicle or a hybrid vehicle, a grommet is installed to a casing for sealing an insertion port of a harness or a piping which is connected to an external portion (refer to Japanese Unexamined Patent Publication Nos. 2002-369346, 2004-72877 and 2009-153264).
In other words, FIG. 20A is an explanatory view showing a typical conventional example. A notch-like grommet installation portion 53 is provided in a wall portion 52 of a casing 51, and a cover 55 is put on the casing 51 and a grommet 54 in a state in which the grommet 54 is installed to the grommet installation portion 53, whereby an insertion port of the harness or the piping is sealed. A through hole 56 for inserting the harness or the piping is provided in the grommet 54.
In this case, the grommet 54 achieves a sealing action by being pinched and compressed between the casing 51 and the cover 55, however, a gap c tends to be generated in a corner portion in a position where respective surfaces of the casing 51, the grommet 54 and the cover 55 intersect (a section where three surfaces are joined together) as shown in FIG. 20B due to a problem on a shape of the grommet 54. Accordingly, there is a case that a seal leakage generates a problem.
Further, the problem of the seal leakage due to the intersection among three members also exists in a connecting position between a cylinder portion of the engine and various covers (refer to Japanese Utility Model Publication Nos. 61-23713 and 61-23714, and Japanese Unexamined Patent Publication No. 2-241956).
Further, there has been proposed a structure which intends to reduce the gap c by arranging a seal projection in a thick surface (a side surface or an upper surface) of the grommet 54, as a prior art, however, there is a case that the gap c can not be done away only by arranging the seal projection as mentioned above, and it is an insufficient countermeasure.